1. Field of the Invention
The present invention relates to an electrostatic powder spray gun of the type which comprises a gun body having a handle on a trigger as well as connections for compressed air and high voltage, a pistol tube secured to the pistol body and an electrode located at the forward end of the pistol tube which is connected to the high-voltage terminal by way of an electrical line extending through the pistol tube and further comprising a powder channel for the powder-air mixture to be sprayed which extends through the pistol tube and discharges axially forward at the forward end thereof as an annular opening coaxial with the longitudinal axis of the pistol tube, and further comprising an auxiliary air line connected to the compressed air connection and extending through the pistol tube and discharging at the forward end thereof.
2. Description of the Prior Art
As principle components, electrostatic powder spray guns comprise a pistol tube from whose mouth a powder-air mixture is output towards the front, and also comprises an electrode arranged in the region of the mouth of the pistol tube and connected to high voltage. In order to be able to influence the shape of the powder jet, it is not only known, but standard, to arrange what is referred to as an impact plate at a defined distance in front of the mouth of the pistol tube, the impact plate usually being mounted at a rod centrally extending through the pistol tube, wherewith the powder jet can then more or less expand to form a powder cloud dependent on the size, shape and distance of the impact plate. It is also known to provide an adjustment structure for the distance of the impact plate from the mouth of the pistol tube, for example the mounting rod may be secured in the pistol body in a screwable manner. One disadvantage of these known powder impact plates is that special manipulations, for example turning a wing nut, are required for adjustment, whereby the adjustment can usually not be carried out during the spraying process, and that the impact plate, even given maximum distance from the mouth of the pistol tube, expands the powder jet, even if not all too greatly, i.e. one does not succeed in producing a focused power jet as is frequently desirable when coating hollow spaces. It is also known to employ auxiliary air jets instead of these mechanical impact plates, in particular in such a manner that the pistol tube is centrally penetrated by a compressed air line ending at a considerable distance in front of the mouth of the pistol tube, this air line being closed at its forward end and comprising discharge bores for the compressed air which are directed obliquely to the rear. The auxiliary air jets emerging from these bores decelerate the powder jet and expand it, i.e. act, so to speak, as a pneumatic impact plate. Here, also, however, special manipulations are required for adjusting the spacing of the bores from the mouth of the pistol tube for the purpose of modifying the shape of the powder cloud and are also required for complete shut-off of the auxiliary air.